(v) Free Fall; Parachutes;
and Paragliders
Limited applications for aerial filming, demanding
custom built camera mounts, and experienced operators.
(vi) Jets
The Lear Jet has been used quite frequently
for IMAX filming, with the camera placed in the nose cone, a special and
very expensive modification. However the Lear Jet has the advantage of
speed and stability and not much restriction on altitude capability. Good
if you have many thousands of pounds to spare per hour of flying time.
(vii) Space Shuttle
As used in IMAX filming; advantages of weightlessness,
and for those high angles of Earth!
2. Rotary
Helicopters are very complex and inherently
unstable. They require delicate and meticulous maintenance, and the rotors
must be balanced, to make them perform adequately for filming purposes.
The advantage of helicopters is that they can land almost anywhere, and
are very manoeuvrable. But these advantages are traded for instability
and vibration. Helicopters are not always available on location, and even
if they are, they are expensive; many times more so than a single engined
fixed wing aircraft per hour; and their range is limited, often requiring
the organisation of fuel dumps prior to working in remote areas. The importance
of stability for an aerial filming platform cannot be over emphasised;
small helicopters and those with only two rotor blades tend to have serious
vibration problems, so if you can afford it go for the larger helicopters
with three, four, or even five rotor blades. Many of the problems associated
with filming from helicopters can be reduced by using special, elaborate
camera mounts; but beware of the blades intruding into shot at the top
of frame when using wide angle lenses out of the door; when you are concentrating
on the choreography and execution of a shot, it can be easy not to see
the rotating blades in your frame, especially if the helicopter pilot
is banking or trying to "crab" sideways - many a beautiful aerial shot
has been ruined by this problem. Helicopters tend to slew, or "fish-tail",
especially at slow speeds, or when flying close to the limit of their
operational envelope. Beware of the hover too - in small helicopters it
tends to be unsteady, and there is always the problem of down draught
which will affect your subject matter, if you are filming close to the
ground. Try to avoid filming during the transition from hover to forward
flight (or vice versa) - when a helicopter is hovering or moving very
slowly it is balancing on a cushion of air; as forward speed increases,
the helicopter moves off the cushion of air and the rotating blades begin
to obtain lifting power by moving into the relative wind. As they do so,
they tend to shudder, causing vibrations that can produce unsteadiness
in a shot. As mentioned earlier, normal vibration levels can be reduced
by balancing of the blades properly - helicopters that do a lot of bush
flying are susceptible to blade strikes by debris or tree branches. While
small nicks in the blades need not necessarily compromise safety, they
can increase vibration considerably. While the vibration limits may be
acceptable to video work, 16 mm or even 35 mm filming, it may be too severe
if you are considering large formats such as IMAX, where the sheer magnification
of the image on to a very big screen also magnifies the unwanted vibration.
At least in the case of large format, room should be made in the budget
to have rotor blades checked and tracked with a strobe light and balanced
with a Chadwick-Helmuth Vibrex system prior to shooting. It is well worth
doing when you consider the cost of re-shoots. It is also worth remembering
that no two aircraft can ever be the same, even if they are of the same
make and model. One will always operate better than another. Even the
best pilot in the world may not be able to coax a poorly performing aircraft
to do what you want it to do in the smooth and fluid fashion you require
for your perfect shot. Plan to execute shots, where possible, into the
prevailing wind. A helicopter will not perform smoothly when flying downwind
or cross wind, no matter how good the pilot is. While availability of
aircraft types is usually the deciding factor on the kind of helicopter
you end up using, it is worth remembering the basic practicalities - the
larger the helicopter, the steadier it will be and there is more room
to organise your equipment, while a small helicopter, such as a Robinson
for example, is very cramped inside, and the skids of a Robinson are high
and wide, making it quite difficult to execute vertical shots.
When working with helicopters, it is worth remembering
a few safety considerations:
- When hovering or manoeuvring at
low speeds near the ground, helicopters recycle the cushion of air that
supports them; the down draught from the blades can cause debris to swirl
upwards and become ingested in the rotor down wash. A simple piece of
plastic, such as a waste bag can destroy a helicopter in seconds by wrapping
itself around a rotor blade. The resulting imbalance renders the helicopter
uncontrollable.
- Keep low when approaching or leaving
a helicopter with the engine running; an unexpected gust of wind can cause
the rotors to sweep close to ground level.
- Avoid the tail rotor; it is invisible
when running. Make it a rule always to work around the front of a helicopter.
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